Clinical outcome after standardized versus dosimetric radioiodine treatment of hyperthyroidism: an equivalence study

The aim of this study was to investigate the equivalence in outcome of stan dardized versus uptake-adjusted dosing of radioactive iodine (I-131) for hy perthyroidism. We performed a 1-year follow-up study of two patient cohorts : 326 patients referred for I treatment of hyperthyroidism in Craves' disea se (GD; n=216) or toxic multinodular goitre (TMG; n=110) in the period June 1995 to January 1998. Of these patients 128 were treated according to a st andardized regimen, based on palpated thyroid volume and diagnosis, and 198 with a I-131 uptake-adjusted dosimetric method. The incidence of hypothyro idism, euthyroidism or recurrence of disease was recorded. in Graves' disea se hypothyroid outcome in the standardized Versus adjusted method was 40.7% vs 44.6% (95% CI difference, -17.4 to +9.5%); it was 67.4% vs 70.8% (95% C I difference -15.9 to +9.3%) for all non-euthyroid outcomes. In TMG, due to wide confidence interval ranges a conclusion of Equivalence could be made only for recurrence of hyperthyroidism (mean -3.2%, 95% CI, -13.8 to +7.5%) . A simplified dosage method for I-131 treatment of hyperthyroidism, which omits I-131 uptake adjustment, may improve procedure efficiency and patient convenience, and leads to an equivalent outcome in GD and probable equival ent outcome in TMG. ((C) 2000 Lippincott Williams & Wilkins).